1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device, and more particularly to the passivation of the periphery of a bonding pad.
2. Description of the Related Art
When a semiconductor device such as a VLSI (very large scale integration) is to be manufactured, a passivation structure is very important around a bonding pad and a bump formed on an electrode pad, and various endeavors have been made to enhance a productivity while maintaining a reliability.
In recent years, a structure using a polyimide resin for a passivation film has variously been proposed. By way of example, as shown in FIG. 21, there are formed an electrode pad 2 comprising an aluminum layer formed to come in contact with a surface of a semiconductor substrate 1 or a wiring layer provided on the surface of the semiconductor substrate, and a bonding pad 5 formed of metal in a contact hole H provided on a silicon nitride film 3 for covering the upper layer of the electrode pad 2 through a TiW layer to be an intermediate layer 4. A polyimide resin film 7 to be a passivation film is formed around the metallic bonding pad 5.
Such a structure is formed through the following manufacturing process.
First of all, a wiring layer (not shown) and an interlayer insulating film (not shown) are formed on the surface of the silicon substrate 1 provided with an element region and a through hole (not shown) is formed by photolithography. Then, the aluminum layer is evaporated and the wiring (not shown) and the electrode pad 2 are subjected to patterning by photolithography. Thereafter, the silicon nitride film 3 is formed on the upper layer of the electrode pad 2 and is subjected to patterning by the photolithography, and a contact hole is formed in the central part of the electrode pad 2 to cover the peripheral edge of the electrode pad 2 with a silicon nitride film (FIG. 22).
As shown in FIG. 23, subsequently, the polyimide resin film 7 to be a passivation film is formed and is subjected to patterning, thereby exposing the electrode pad 2 as shown in FIG. 24.
If the aluminum layer is exposed to a surface, it is apt to be corroded. As shown in FIG. 25, therefore, a titanium tungsten TiW film to be a barrier layer is formed as the intermediate layer 4 on the aluminum layer by the sputtering method and the metal layer 5 to be a bonding pad is then formed.
As shown in FIG. 26, thereafter, the metal layer 5 and the intermediate layer 4 are subjected to patterning by the photolithography.
Accordingly, it is desirable that the edge of the pad layer 5 is coincident with that of the polyimide resin film 7. In consideration of mask precision, there is a problem in that the edges are coincident with difficulty. On the other hand, there is a problem in that a short circuit is apt to be caused if the metal layer 5 and the intermediate layer 4 get over the passivation film 7. For this reason, the patterning is carried out in consideration of precision in the photolithography.
Consequently, a clearance is generated between the polyimide resin film constituting the passivation film and the pad layer 5 so that TiW which is easily oxidized is exposed. For this reason, there is a problem in that corrosion is apt to be caused, the passivation effect cannot be obtained well and the reliability is thereby deteriorated.
[Problems that the Invention is to Solve]
In the conventional pad structure, thus, there is a problem in that a water content enters from the clearance between the passivation film and the bonding pad layer, the electrode pad such as aluminum is easily corroded and the reliability is thereby maintained with difficulty.
The invention has been made in consideration of the circumstances and has an object to provide a semiconductor device comprising a bonding pad having a passivation structure in which a resistance to a water content is high and a reliability is enhanced.
A first aspect of the invention is directed to a semiconductor device comprising a semiconductor substrate provided with a desirable element region, an electrode pad formed to come in contact with a surface of the semiconductor substrate or a wiring layer provided on the surface of the semiconductor substrate, a bonding pad formed on a surface of the electrode pad through an intermediate layer, and a resin insulating film for covering a peripheral edge of the bonding pad such that an interface of the bonding pad and the intermediate layer is not exposed to a side wall.
According to such a structure, the resin insulating film is formed to cover the peripheral edge of the bonding pad. Therefore, the electrode pad and the intermediate layer which are provided as lower layers are not exposed but covered with the resin insulating film. Consequently, a reliability can be enhanced.
The intermediate layer includes a barrier metal layer such as TiW, an adhesion layer or a lower layer constituting a plated substrate. The invention is particularly effective in the case in which the layers are corrosive or are formed of materials which are easily oxidized.
It is desirable that the resin insulating film should be a polyimide resin film.
According to such a structure, it is possible to obtain a pad structure having a high reliability which can produce the insulation of the surface of the peripheral edge in the bonding pad and a passivation effect by using the polyimide resin film.
It is desirable that the resin insulating film should be formed to cover edges of the bonding pad and the intermediate layer.
According to such a structure, it is possible to obtain a bonding pad structure having a high reliability.
It is desirable that the intermediate layer should include a titanium tungsten (TiW) layer.
According to such a structure, there is such a drawback that the titanium tungsten (TiW) layer is particularly oxidized easily and a deterioration is apt to be caused if the interface is exposed. According to the invention, however, it is possible to easily obtain a bump structure having a high reliability.
It is desirable that the bonding pad should be formed of metal.
According to such a structure, it is possible to obtain a semiconductor device having an excellent bonding property and a high reliability.
It is desirable that the electrode pad should be formed by a metal film containing aluminum.
There is such a drawback that the aluminum layer is particularly oxidized easily and a deterioration is apt to be caused if the interface is exposed. According to such a structure, however, it is possible to easily obtain a pad structure having a high reliability.
It is desirable that the electrode pad should be a thin copper film.
There is such a drawback that the copper layer is particularly oxidized easily and a deterioration is apt to be caused if the interface is exposed. According to such a structure, it is possible to easily obtain a pad structure having a high reliability.
It is desirable that a semiconductor device should comprise a semiconductor substrate provided with a desirable element region, a first electrode pad formed to come in contact with a surface of the semiconductor substrate or a wiring layer provided on the surface of the semiconductor substrate, a bonding pad formed on a surface of the first electrode pad, a bump formed through an intermediate layer on a surface of a second electrode pad provided on the semiconductor substrate, and a resin insulating film formed in at least a peripheral portion of the bump and a peripheral portion of the bonding pad to cover a peripheral edge of the bonding pad such that an interface of the bonding pad and the first electrode pad is not exposed to a side wall, and to cover an interface of the bump and the intermediate layer which is exposed to a side surface of the bump.
According to such a structure, it is possible to provide a pad structure having a high reliability also in a semiconductor device in which wire bonding and direct bonding using a bump are mixed.
The invention provides a method of manufacturing a semiconductor device comprising the steps of forming an electrode pad to come in contact with a surface of a semiconductor substrate provided with a desirable element region or a wiring layer provided on the surface of the semiconductor substrate, forming an intermediate layer on a surface of the electrode pad, forming a pad layer to be a bonding pad on a surface of the intermediate layer and patterning the intermediate layer and the pad layer, and forming a resin insulating film to cover edges of patterns of the bonding pad and the intermediate layer.
According to such a structure, the pad layer is formed and patterned and the polyimide resin film is then formed. Therefore, the peripheral edge of the pad can be covered well.
It is desirable that the step of forming a resin insulating film should include a step of applying a polyimide resin film.
According to such a structure, the resin insulating film is the polyimide resin film. Therefore, it is possible to obtain a surface structure which can easily be formed and has the greatest passivation effect.
It is desirable that the step of forming an intermediate layer should include a step of forming a titanium tungsten (TiW) layer by a sputtering method.
While there is such a drawback that the titanium tungsten (TiW) layer is particularly oxidized easily and a deterioration is apt to be caused if the interface is exposed. According to such a structure, however, it is possible to easily obtain a bump structure having a high reliability.
It is desirable that the step of forming a pad layer should include a step of forming a metal layer by sputtering.
According to such a structure, the metallic bonding pad can be formed more efficiently.